Rugers off the Radar The GP100 Revolvers

John Robinson
Rugers off the Radar
The GP100 Revolvers
For Australian handgunners,
whose only legal justification
for owning a handgun is
target shooting, when it
comes to centrefire revolvers,
Ruger double-action sixguns
hardly rate a mention and
are relatively infrequent
competitors on the firing line.
R
uger made its start building revolvers
with the introduction of its Blackhawk single action pistols in the
1950’s, with outsiders predicting failure of that type od handgun. Colt’s Peacemaker had been discontinued, and the development of high powered autoloaders and a raft of
double action revolvers were seen as the future
of the handgun industry. More than 50 years
later, the Blackhawk is still around.
In 1972, Ruger introduced its own doubleaction “Six Series” revolvers- first the Security Six followed by the Service Six and
Speed Six . Like the Blackhawk revolvers,
the new DA models were built around investment cast “medium” size frames, used
music wire (coil) springs throughout for enhanced reliability and a transfer bar to ensure safety against accidental discharge.
Like all Ruger firearms, they were reliable,
well made and affordable, intended principally at the police, military and civilian selfdefense markets, these were six shot, .38
Special and .357 Magnum (later 9x19mm
and .38 S&W, swing out cylinder, hand ejector, police service style revolvers.
Over 1,500,000 Six series revolvers were sold
by the time the line was discontinued in 1988.
In its place, the GP100, introduced in
1985, raised the bar further with its heavier
frame and very robust construction around
the .357 Magnum cartridge.
Maybe Ruger had a look at the success of
S&W’s medium frame 586 L Frame revolvers
and observed that building .357 Magnums on
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The test pistols; 4”and 6”GP100’s are
very well finished and rugged revolvers.
smaller frame revolvers was not the way to go.
The S&W Model 19 .357’s built on the smaller K frame is good example of how to loosen
up a sixgun with a steady diet of heavy loads.
The GP100 uses a larger frame than the Six
Series and incorporates some major improvements. First is the cylinder locking system,
which is latched to the frame at the crane, as
well as at the back of the ejector rod.
There is a blade that protrudes from the
front of the crane that is operated via the
cylinder axle. As the rear pin of the axle
slides across the recoil shield, it is pushed
forward and a linkage retracts the front
locking blade. When the cylinder is fully
closed, the cylinder locks into the frame at
both ends. It is a very solid, double-ended
locking system that cannot be found on
any other revolver.
The GP100 also has a stubby grip frame
that replaces the conventional rev olver grip
frame, allowing the attachment of a onepiece grip of practically any size, shape or
style. Dan Wesson revolvers have a similar
arrangement. The grip panels don’t attach
to the sides of the GP100’s grip frame, as
with traditional revolvers. Instead, a onepiece grip slides over it and is attached by a
screw through the bottom of the grip.
Coil springs are used exclusively. Another
unique feature of the GP100 is its ingenious
frame design compared to other double action revolver brands. The investment cast
frame has no removable side plate. Both
sides of the frame are solid and symmetrical
and the assembly is very clever, with the
trigger group fitting as a unit into the underside of the frame.
The fitting of the trigger group to the
frame is very precise, to the point that it
takes a very hard look to see the joint between the two components.
OCTOBER/DECEMBER 2013
SPECS
RUGER GP100 REVOLVERS
Manufacturer:
Sturm Ruger
Model:
GP100
Material:
Stainless steel.
Calibre:
.357 Magnum (.38 Special)
Barrel length:
4”and 6” tested
(3” also available)
Rifling twist:
1:475mm (1: 18 3/4”)
Sights:
Fully adjustable
Action:
Double action/single action.
Cylinder capacity:
6
Trigger pull:
Approx. 1500g single action,
4000g double action
Length:
4”- 245mm, 6” - 295mm
Weight:
4” – 1140g, 6”- 1170g
RRP:
$900 – shop around
Distributor:
Nioa (www.nioa.com.au)
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It would be a safe bet to put any amount of
money on a challenge for anyone to disassemble the GP100 with first reading the instruction on how to do it. Once revealed it is
very simple, but must have taken a high degree of design precision.
The grip needs to be removed (the test pistols are fitted with Hogue grips as standard) to
start the take-down. The hammer needs to be
cocked and the hammer spring strut moves far
enough through the stirrup to expose the hole
in the strut. A small pin needs to be put in the
hole and when the hammer is lowered, the
spring remain captive on the strut and allows
the strut and spring assembly to be taken out.
With this out, the hammer pivot pin can be
pushed out of the frame to the right and the
hammer can be pulled out of the frame. The
next part is the tricky bit. There is a slot in the
grip frame and using a flat ended thin rod
(screw driver), the retaining plunger that holds
the trigger group is depressed. This has a very
strong spring and takes a bit of effort.
This allows the rear of the trigger group to
be swung down out of the frame. With the
trigger group out, the cylinder and crane can
be removed from the frame. It is hard to imagine the somewhat complex but functionally very effective parts that make this system work, being made without Ruger’s
expertise in investment casting.
The GP100 revolvers come in three barrel
length, nominally 3”, 4” and 6” and Nioa was
kind enough to send me not one, but two
GP100’s to test for GUNS; a 4” and a 6”. The
satin finished stainless revolvers are good
looking handguns, with their solid frames
and full under lug barrels. 6” and 4” double
action revolvers have a spot in the pistol
match program for the Service Pistol matches
and 1920 and 1500 events. A 4” revolver is a
necessity for 25m Service as maximum barrel
length is mandated at 4” (100mm).
Both GP100’s had reasonably good double
action trigger pulls out of the box with a smooth
and consistent DA pulling off at about 4-5kg.
The single action trigger weight was also similar
on both revolvers, releasing at about 1500g.
The sights on the GP100’s are adjustable
but I would not rate the rear sights very
highly, although they work OK. Most Ruger
revolver sights are similar, and those using
Rugers for serious target shooting often replace the rear sight with an after-market option. I have done this with my Ruger Blackhawk silhouette pistol. The windage
adjustment requires a very small screwdriver
while the elevation adjustment screw is
OCTOBER/DECEMBER 2013
much larger. While the adjustments are a bit hard to get on with,
the sights otherwise work very well
with the white outline rear blade and 3mm
wide front sight. The front sight element is
removable and is retained on the barrel with
a set screw above the Ruger’s muzzle
The GP100’s are very well put together.
The cylinders lock up with no side play and
the cylinder latching arrangements also
highlights another clever design incorporated in these revolvers. All other revolvers
have their cylinder latch slots located over
each cylinder. This results in a thin area
right over the thinnest part of the cylinder.
The Ruger GP100 has its cylinder latch offset, so that the cut-out is located at a thicker
part of the cylinder wall.
What started as a routine set of shooting
tests turned into a number of visits to the
range, numerous handloading sessions and
some head scratching in coming to grips
with the performance of both these pistols.
I could not get either pistol to group better
than about 75mm at 25m with my Service
Match handloads that are used in my two
696 S&W’s, also a 4”and a 6”. These loads
use 125gn conicals over 4.8gn Bullseye powder and shoot well in the Smiths, although
the 6” S&W did not like lighter (3.5gn Bullseye) loads very much.
I tried some other 125gn, 135gn and
200gn projectiles with various powder
charges, as well as some hollow based wadcutters with 3.0gn Bullseye loads and was
not happy with their performance either.
The hollow based wadcutters were fairly old
stock and very soft, and cause some leading
problems with both Rugers.
I did some measurements on both GP100’s
and found that the chamber throats on each
revolver measured 0.360” and the bore diameter on each was a whisker over .358”.
The projectiles used in the first test sessions
were all .3565”- .357”. A check through my
projectile collection came up with some
OCTOBER/DECEMBER 2013
150gn homecast
RCBS
Keith-type bullets, some copperclad hollow based wadcutters that were
harder than the first batch (brand unknown) and some 200gn Copper Hawk projectiles that all measured .358”. A similar
Bullseye charge was used with the two card
cast projectiles, and 3.0gn loads were used
with the copper plated wadcutters.
At last, some reasonable groups were delivered by both Rugers – the best being
around 50mm at 25m. No more leading
problems were observed with any of these
loads. Over the course of testing the
GP100’s, eight different types of projectiles
were tried with three different powder
charges (all Bullseye) to get to the end game.
The good news with all this was that the
GP100’s could produce reasonable results given
appropriate ammunition. For prospective owners, the bullet diameter issue is a vital factor in
getting acceptable target accuracy out of these
revolvers. Commercial bullet makers list the
bullet diameter on their packaging but this is
not always accurate. The Top Score 200gn
loads that were listed as .357” were measured at
.356” and another brand listed at .358 measured
only .3565”. Hawkesbury River Bullet Company
will size its hard cast projectiles to you specifications (within reasonable limits). Casting your
own is another option and I have done thyat
with some of my revolver loads, with the option
of sizing projectiles to .359”.
The Ruger GP100 is a very well built double action revolver, and it is a pity that we
are not allowed to acquire handguns for
other recreational shooting purposes, as the
rugged reliability and strength built into
these revolvers would see them deliver a lifetime of hard service.
OPPOSITE PAGE:
TOP: A critical dimension – both
GP100’s has .360 chamber throats and
projectiles need to accommodate this
dimension.
ABOVE INSERT: Another unique Ruger
feature – the offset cylinder latch moves
the cut-out on the cylinder away from
the thinnest section of the cylinder wall.
BOTTOM LEFT: Coil springs deliver a
smooth and consistent double action
trigger on the Rugers and the GP100’s
adequate weight keeps recoil movement
under control.
BOTTOM INSERT: Accuracy testing off
a sandbag rest – the GP100 sight
deliver a good sight picture.
CURRENT PAGE:
TOP INSERT: The large front locking
latch on the GP100’s is another unique
Ruger feature that ensured solid lock-up
of the cylinder at both ends.
TOP RIGHT: Very clever design; no side
plate for a solid frame and the trigger
group comes out as an assembly. Coil
springs used throughout.
ABOVE LEFT: The Ruger GP100 4”.
Hogue grips are standard on all GP’s.
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